1. Field of the Invention
This invention is related to the treatment of used drilling fluid to separate its various components and produce re-usable fluid; and, in certain particular aspects, to methods and equipment for removing hydrated clays or “gumbo” from drilling fluid.
2. Description of Related Art
In drilling wells it is common to circulate drilling fluid or “mud” down a wellbore in progress to remove drilled cuttings or “drilled solids” from the wellbore. At the surface the mud is separated from the drilled solids so that the mud can be re-used by re-circulating the cleaned mud back down into the wellbore. The prior art discloses a variety of machines and apparatuses used to clean drilling mud, including, e.g., centrifuges, shale shakers, and gumbo separators.
Gummy hydrated clay or “gumbo” in a formation through which a wellbore is being drilled can adhere to equipment, agglomerate in large solid masses, and can clog and blind screens and other separation equipment. Some prior art efforts to deal with gumbo have included using chemical additives to change the properties of drilling mud, but this adds cost to the drilling expense. In other prior art systems the vibrational amplitude of a shale shaker is increased and various types of water sprays are used, but often the gumbo simply forms a new steady state gumbo mass at the new operating conditions. Specialized coatings have been applied to screens, e.g. as described in U.S. Pat. No. 3,963,605, but these coatings add cost to the screening equipment, and can be worn off the screens. U.S. Pat. No. 5,921,399 discloses apparatus used in conjunction with, and upstream of, existing mud cleaning equipment that removes gumbo from drilling mud before drilling cuttings are removed from the mud.